The behavior of Vbeta2(+) T cells reactive with the pathogenic superantigen toxic shock syndrome toxin-1 (TSST-1) was examined in 12 patients with neonatal TSS-like exanthematous disease (NTED). In 8 patients, the percentage of Vbeta2(+) T cells in peripheral blood (PB) T cells had increased to three times the level in methicillin-resistant Staphylococcus aureus (MRSA)-free neonatal controls, when examined on days 4 to 7 of life. In the remaining 4 patients, however, the percentage of Vbeta2(+) T cells was significantly low, i.e., ranging from less than 10% to 30% of the control level, when they were examined on days 4 to 8 of life, and the percentage increased dramatically several days later, indicating that these patients actually had NTED. We recommend that, in patients who are suspected of having NTED, when an increase in Vbeta2(+) T cells is not observed in a comparatively early period of the illness, reassessment of the Vbeta2(+) T cells should be carried out 2 to 4 days later, to obtain a conclusive diagnosis of NTED.